What breed of horse is small hardy and always chestnut or sorrel with a flaxen mane tail?

The breed of horse you're describing is most likely the Welsh Pony.

Here's why:

* Small and Hardy: Welsh Ponies are known for their sturdy build and hardiness, being able to thrive in various conditions.

* Chestnut or Sorrel: While they can come in other colors, chestnut and sorrel are very common colors for Welsh Ponies.

* Flaxen Mane and Tail: A flaxen mane and tail are a defining characteristic of many Welsh Ponies, especially those with chestnut or sorrel coats.

Important Note: It's worth remembering that while these are typical characteristics, there can be variations within the breed. Some Welsh Ponies might be a different color, or their mane and tail might not be flaxen.